The energy company reported net income of $122 million, or $1.10 per share, compared with $149.1 million, or $1.35 per share, in the year-earlier quarter.

For all of fiscal 2012, Alliant revised its earnings forecast to $2.73 to $2.87 per share, down from its previous forecast of $2.75 to $2.87 per share. It was slightly also slightly lower than the consensus estimate of Wall Street analysts, which had been $2.91 per share.

A loss on a solar energy project at Alliant's RMT renewable energy subsidiary was the largest single factor in downward earnings swing. The company's non-regulated businesses took a 13-cent loss for the quarter, due mainly to a "subcontractor performance failure" on a solar project in New Jersey.

Alliant's utility operations generated earings of $1.35 per share, up from $1.32 in the third quarter of 2010.Factors adding to the improvement included stronger power demand for air conditioning due to hot weather, and favorable effects of a tax credit rider at Interstate Power & Light.